The present invention relates to intra-vehicular communication systems, and more particularly, to arrangements for communicating data and supplying power through the same interface in a vehicle.
Demands for communication systems within vehicles have increased with greater use of electronic modules for a multitude of functions. Moreover, the increasing demand for data transmission within a vehicle creates a problem for managing wiring among functional modules. For example, many wires are typically needed to accommodate the power and communication requirements of an internal controller, an outside mirror position switch in a door panel, and the outside mirror itself. This is especially so if the outside mirror assembly includes several electrical components having differing functions, such as turn signal indicators, mirror positioners, an electrochromic mirror, RF antennas, a glass heater, security lights, and road/lane edge location sensors. If an outside mirror assembly included all these components and also included a mirror position memory feature, as many as 20 wires may be required to be run to the outside mirror. Good wire management suggests that it is desirable to reduce as much as possible the number of wires that must be run to the outside mirror assembly and to other electronic modules in the vehicle as well.
To reduce some of the wiring required for much of the electronic modules in an automobile, many automobiles have a dedicated bus for electrical signals related to the power train, and in addition, have at least one CAN or J1850 type system bus for other power demands within the vehicle such as locks, windows, HVAC, and the like. With such bus communication systems, however, each electronic module separately receives power from a power supply of the vehicle, such as the vehicle battery or ignition. Thus, in addition to the bus wiring, separate wiring must be run to each module and electrical component to provide power.
While replacing discrete wiring systems with bus systems has significantly reduced vehicle manufacturing and material costs, there are some situations in which it has generally not been desirable to replace discrete wiring with a connection to the CAN or J1850 vehicle system bus. For example, running the vehicle system bus to the exterior of the vehicle for connection to an outside mirror assembly or to any other electronic module outside the vehicle may compromise vehicle security. More specifically, commands to unlock the vehicle doors and deactivate the vehicle alarm system are typically transmitted over the vehicle system bus. If this bus were run to an electronic module outside the vehicle, a thief could readily gain access to the bus and transmit a command on the bus causing the doors to unlock and the alarm to deactivate. For this reason alone, manufacturers have not connected the electronic module in an outside rearview mirror assembly to a bus, but instead have used a significant number of discrete wires to enable independent control of all the functional components in the assembly.
It is known to use ordinary residential power lines to transmit data in a building. Such communication is affected by superimposing data signals on a power line using orthogonal frequency division multiplexing to accommodate noise and other interference in the power line. It is further known to apply this technology to data transmission in a tractor-trailer combination over the existing DC power bus in order to avoid extra wires beyond the standard SAE J560 connector. This data transmission technique, however, does not address the situation often found in automobiles where there is insufficient bandwidth to carry both power and data simultaneously or where using the vehicle bus would compromise security as in communication with an outside mirror. Also, if such a data transmission technique were used in an automobile, the resultant system would produce unacceptable levels of electromagnetic interference (EMI) since the data signals would be transmitted through the unshielded power wiring that runs through most of the vehicle. There remains a need for a bi-directional communication system, especially between the inside of the vehicle and the outside of the vehicle, which will accommodate a solution to the foregoing problems.
An additional problem caused by increasing vehicle complexity arises from the use vehicular windows, which incorporate low-E metallic coatings in order to reduce solar heating inside vehicles. While this feature has been effective in solar control, it has the unfortunate side effect of RF shielding the interior of the vehicle. As a result, the effectiveness of RF-based systems where the antenna is located in the interior of the vehicle, such as remote keyless entry, garage door openers, and tire pressure monitoring systems, is reduced.